This invention relates to nuclear reactors and has particular relationship to the sleeving of damaged or corroded tubes of a steam generator of a nuclear reactor. Damaged tubes are sleeved by inserting sleeve blanks into the tubes. For insertion, a sleeve blank is mounted on a mandrel. The sleeve blank and mandrel is referred to herein as a "sleeving assembly".
The tubes of a steam generator are sealed through a tube sheet from the bottom of which a channel head extends. Damaged tubes are accessible for sleeving from within the channel head. The channel head may be entered through a manway. The region within the channel head is radioactive and it is desired to minimize the exposure of personnel to radioactivity within the channel head during a sleeving operation.
U.S. Pat. No. 4,463,994 granted Feb. 3, 1987 to Frank W. Cooper et al. for Suspension of Tools for Sleeving of Tubes of Steam Generator (herein Cooper) and assigned to Westinghouse Electric Corporation is typical of the prior art. Cooper has performed highly satisfactorily. However, its operation demands that personnel be exposed to radioactivity for short intervals within the channel head. There is an additional drawback to Cooper. The channel head is a semi-sphere so that as the periphery of the tube sheet is approached, the channel head avails less and less vertical space for a sleeve-blank insertion operation. The Cooper sleeve-blank insertion apparatus vertical space is of such length that the area of the tube sheet over which it can sleeve damaged tubes is restricted.
There has become available a robotic manipulator tool which is referred to as Remote Operated Service Arm or ROSA. In the process of creating this invention, it has been realized that ROSA can be loaded with sleeving apparatus or a sleeving tool externally of the channel head and may then be controlled, from a control station outside of the channel head, so that it moves the tool into the channel head and positions the tool for a sleeving operation. The insertion into the channel head and sleeving operation of the tool may then be controlled from a station external to the channel head. By external control of the tool, the mandrel may then be withdrawn preparatory to another sleeving operation.
A ROSA has a plurality of arms between which actuators for moving the arms in different directions are interposed. A typical actuator is disclosed in U.S. Pat. No. 4,398,110, Flinchbaugh et al. (herein Flinchbaugh). A ROSA of practicable dimensions and structurer can manipulate a load of limited weight, typically about 50 pounds. A greater weight might result in deformation of its arms and damage to motors, brakes, tachometers, resolvers, or other parts of the actuators. A disadvantage of the Cooper apparatus and other prior-art apparatus is that its weight exceeds the weight which can be handled by a ROSA.
It is an object of this invention to overcome the drawbacks and disadvantages of the prior art and to provide apparatus for a tool for inserting a sleeve blank into a damaged tube of a steam generator of a nuclear reactor, or into a tube of any other like tubular apparatus, which tool shall be capable of being manipulated by a ROSA of reasonable weight, dimensions and structure. Specifically, it is an object of this invention to provide sleeve-blank insertion apparatus having a total weight of less than 50 pounds. Another object of this invention is to provide a sleeve-insertion apparatus which shall be capable of inserting sleeve blanks into tubes of a steam generator which are located over a greater area of the tube sheet than is within the capability of prior-art sleeve-blank insertion apparatus.
It is also an object of this invention to provide a method for inserting a sleeve blank into a damaged tube of a steam generator in whose practices the disadvantages of the prior art shall be eliminated.